docker: allow configuring http proxy via env variables

Dockerfile

@@ -12,6 +12,9 @@ RUN adduser -D -h /usr/local/searx -s /bin/sh searx searx \
  && echo 'sed -i "s|base_url : False|base_url : $BASE_URL|g" searx/settings.yml' >> run.sh \
  && echo 'sed -i "s/image_proxy : False/image_proxy : $IMAGE_PROXY/g" searx/settings.yml' >> run.sh \
  && echo 'sed -i "s/ultrasecretkey/`openssl rand -hex 16`/g" searx/settings.yml' >> run.sh \
+ && echo 'if [ -n "$HTTP_PROXY_URL" ] || [ -n "$HTTPS_PROXY_URL" ]; then' >> run.sh \
+ && echo '  sed -i "s~^#    proxies :~    proxies:\\n      http: ${HTTP_PROXY_URL}\\n      https: ${HTTPS_PROXY_URL}\\n~" searx/settings.yml' >> run.sh \
+ && echo 'fi' >> run.sh \
  && echo 'python searx/webapp.py' >> run.sh \
  && chmod +x run.sh